著者
Norikazu MATSUOKA Shin-ichi SAWAGUCHI Kenji YOSHIKAWA
出版者
The Association of Japanese Geographers
雑誌
地理学評論 (ISSN:13479555)
巻号頁・発行日
vol.77, no.5, pp.276-300, 2004-04-01 (Released:2008-12-25)
参考文献数
62
被引用文献数
11 12

This report overviews observations on periglacial geomorphology in central Spitsbergen, which have been undertaken by the Japanese geomorphological groups. Focus is given to permafrost-related processes, including solifluction, thermal contraction cracking and pingo growth. Annual freeze-thaw action dominates the ground, resulting in extensive occurrence of solifluction and shallow landslides on soil slopes. Solifluction shows low surface velocity but large volumetric transport, which respectively reflects infrequent diurnal frost creep and deep movement. The latter partly originates from plug-like flow in the basal active layer, where permafrost temperature is low and muddy sediment is thick. Non-sorted polygons with a wide range of diameters develop on lowlands. In colder inland terrains, large polygons (>7m) have ice wedges, whereas smaller polygons have only soil wedges or cracks confined to the active layer. Significant ice-wedge cracking occurs during rapid and intensive cooling in midwinter. In warmer coastal terrains, ice wedges are not common even below large polygons, because higher winter temperature can produce only shallow cracks. Open-system pingos occur in valley bottoms and near shores. Some pingos are still growing under a low artesian pressure fed by constant supply of sub-permafrost water. Following lateral river erosion, a new frost mound emerged at a side of a pingo, reaching 3m high during three years. The observations demonstrate that central Spitsbergen is situated in a High Arctic but relatively warm permafrost environment. The transitional condition between cold and warm permafrost allows diverse periglacial features to coexist within a small area. Even minor climatic change can switch the two thermal regimes, affecting significantly the type and magnitude of periglacial processes.
著者
Atsushi IKEDA Tetsuo SUEYOSHI Norikazu MATSUOKA Takemasa ISHII Youhei UCHIDA
出版者
The Association of Japanese Geographers
雑誌
地理学評論 (ISSN:13479555)
巻号頁・発行日
vol.80, no.5, pp.259-271, 2007-04-01 (Released:2010-03-12)
参考文献数
32
被引用文献数
1 1

Present-day distribution and ongoing degradation of permafrost were evaluated by geophysical means in the source area of the Yellow River, located at the northeastern margin of the Tibetan Plateau. Seismic, electrical and/or thermal soundings were undertaken at 15 sites between 3260m and 4790m ASL in 2003-2005. High P-wave velocities (>2kms-1) and relatively high DC resistivities (650-1100Ωm) below a thin uppermost layer show that permafrost 10-30m in thickness occurs above 4300m ASL. In contrast, low P-wave velocities (<1kms-1) throughout the uppermost ten to fifteen meters of sediments indicate that permafrost is absent below 4000m ASL. On widespread alluvial plains between 4200m and 4300m ASL, some sites show subsurface intermediate P-wave velocities (1.5-1.7kms-1) and low resistivities (30-140Ωm) indicating the presence of unfrozen-saturated sediments, while others show high DC resistivities possibly indicating the presence of permafrost. Negative values of the mean annual ground surface temperature (MAST) also indicate widespread permafrost only above 4300m ASL under the present climatic condition. Assuming that the inter-annual variation in MAST follows that in the mean annual air temperature, permafrost is estimated to have significantly thawed on the alluvial plains at 4200-4300m ASL during the last half-century.
著者
岩田 修二 白石 和行 海老名 頼利 松岡 憲知 豊島 剛志 大和田 正明 長谷川 裕彦 Decleir Hugo Pattyn Shuji Iwata Kazuyuki Shiraishi Yoritoshi Ebina Norikazu Matsuoka Tsuyoshi Toyoshima Masaaki Owada Hirohiko Hasegawa Hugo Decleir Frank Pattyn
雑誌
南極資料 = Antarctic Record (ISSN:00857289)
巻号頁・発行日
vol.35, no.3, pp.355-401, 1991-11

第32次南極地域観測隊(JARE-32)夏隊のセールロンダーネ山地地学調査隊は, 1990年12月24日あすか観測拠点を出発し, 1991年2月7日に再び「あすか」に帰り着くまでセールロンダーネ山地中央部で, 地形・地質・雪氷調査を行い測地作業も実施した。雪上車とスノーモービルを利用してキャンプを移動しながら調査するという従来と同じ行動様式をとったため, 設営面でもおおかたはこれまでの方式と同じである。地学調査は, 地形では, 野外実験地の撤収, 岩石の風化の調査, モレーン・ティルのマッピング, 地質では, 構成岩石の形成順序の解明, 構造地質学的・構造岩石学的そして地球化学的研究のためのサンプリング, 測地では, 重力測量, 地磁気測量, GPSによる基準点測量が行われた。ベルギーからの交換科学者は氷河流動・氷厚などを測定した。The Sor Rondane field party as part of the summer party of the 32nd Japanese Antarctic Research Expedition (JARE-32) carried out geomorphological, geological, geodetic, and glaciological fieldworks in the central area of the Sor Rondane Mountains for 45 days from December 24,1990 to February 7,1991. The field trip was conducted by two parties, consisting of 9 persons, traveling from mountains to mountains to shift tented camps using 4 snow vehicles towing their equipments on sledges behind. Nine snowmobiles (motor toboggans) were used for their field researches on glaciers. Geomorphologists carried out measurements in the periglacial field experimental sites, observations of rock weathering, and mapping of chronological sequence of tills and moraines. Geologists studied chronological sequence of rock formation and collected rock specimens for structural, petrological, and chemical analyses. A surveyor set up geodetic control stations using GPS satellite positioning system and made gravity surveys on glaciers as well as at some control stations. Two Belgian glaciologists took part in the fieldwork as exchange scientists and studied dynamics of glacier movement and ice thickness.